Effect of age on female choice in the field cricket, Gryllus interger

Female choice is an important element of sexual selection that may vary among females of the same species. Few researchers have investigated the causes of variation in selectivity with respect to potential mates and overall level of motivation toward a stimulus source representative of a mate. This study demonstrates that female age may be one cause of variation in female choice. Females of different ages may have different mate preferences. As females age, they have less time left to reproduce, and their residual reproductive value decreases. This should correspond to a higher reproductive effort which may be represented as increased motivation and/or decreased selectivity. The effect of age on mate choice in Gryllus integer was investigated by using a non-compensating treadmill, called the Kugel, to measure female phonotaxis. Artificially generated male calling songs of varying pulse rates were broadcast in either a singlestimulus or a three-stimulus experimental design. The pulse rates used in the calling song stimuli were 70, 64, 76, 55 and 85 pulses per second. These corresponded to the documented mean pulse rate for the species at the experimental temperature, one standard deviation below and above the mean, and 2.5 standard deviations below and above the mean, respectively. Test females were either 11-14 days or 25-28 days post-ecdysis. Trials usually were conducted two to seven hours into the scotophase. In the single-stimulus experiment, females were presented with stimuli with only one pulse rate. Older females achieved higher vector scores than younger females, indicating that older females are more motivated to mate. Both groups showed little phonotactic response towards 55 or 85 pIs, both of which lie outside the natural range of G. integer calling song at the experimental temperature. Neither group discriminated among the three pulse rates that fell within the natural range of calling song. In the three-stimulus experiment, females were presented with stimuli with one of three pulse rates, 64, 70 or 76 pIs, In alternation. Both age groups had reduced responsiveness in this experiment, perhaps due to an increase in perceived male density. Additionally, younger females responded significantly more to 64 and 70 pIs than to the higher pulse rate, indicating that they are selective with respect to mate choice. Older females did not discriminate among the three pulse rates. Therefore, it was concluded that selectivity decreases with age. A further study was conducted to determine that these effects were due to age and not due to the differing periods without a mating between the two age groups. Again, stimuli were presented in a three-stimulus experimental design. Age was held constant at 28 days and time since last mating varied from 11 to 25 days. Females varyIng in time since last mating did not differ in their responses to the calling song pulse rates. This indicated that the increased motivation and decreased selectivity exhibited In the initial experiments were due to age and not to time without a mating. Neither time of trial nor female weight had an effect upon female phonotaxis. Data are discussed in terms of mate choice, residual reproductive value, and costs of choice.

The effect of diet and parasite load on female phonotaxis in the Texas field cricket, Gryllus integer

Female crickets respond selectively to variations in species-specific male calling songs. This selectivity has been shown to be age-dependent; older females are less choosy. However, female quality should also affect female selectivity. The effect of female quality on mate choice was examined in Gryllus integer by comparing the phonotactic responses of females on different diets and with different parasite loads to various synthetic models of conspecific calling song. Test females were virgin, 11-14 days old, and had been maintained on one of five diets varying in protein and fat content. Phonotaxis was quantified using a non-compensating Kugel treadmill which generates vector scores incorporating the speed and direction of movement of each female. Test females were presented with four calling song models which differed in pulse rate, but were still within the natural range of the species for the experimental temperature. After testing, females were dissected and the number of gregarine parasites within the digestive tract counted. There were no significant effects of either diet or parasitism on female motivation to mate although the combined effects of these variables seem to have an effect with no apparent trend. Control females did not discriminate among song types, but there was a trend of female preferences for lower pulse rates which are closest to the mean pulse rate for the species. Heavily parasitized females did not discriminate among pulse rates altho~gh there was a similar trend of high vector scores for low pulse rates. Diet, however, affected selectivity with poorly-fed females showing significantly high vector scores for pulse rates near the species mean. Such findings raise interesting questions about energy allocation and costs and risks of phonotaxis and mate choice in acoustic Orthoptera. These results are discussed in terms of sexual selection and female mate choice.

The effect of gregarine parasite infections, age, and diet on calling song structure and mating behaviour in the Texas field cricket, Gryllus integer

In the past ten years, many researchers have focussed their attention on parasites regarding the role they may play in causing variations in male secondary sexual traits and subsequent effects on female choice. Male age has also been suggested to be an important factor in female choice if old age reflects superior genes. This study investigated the effects that gregarine gut parasites, age, and diet have on the calling and mating behaviour of the male Texas field cricket, Gryllus integer. Male calling songs were recorded in the laboratory using a Digital Signal Processing Network. The song parameters measured were: pulse rate, pulse width, burst duration, pulses per burst, interburst interval, and percent missing pulses. The effects of parasite load and age on the various calling song parameters was investigated in crickets that were fed two different diets varying in nutritional quality. None of the calling song parameters were affected by either parasite load or age in either diet grou p. Courtship behaviour was ob served and recorded using an Eventlog recorder on an IBM computer in the laboratory. Females mated equally with paras(tized and unparasitized males and with old and young males The total duration and proportion of time spent performing each of 9 courtship displays were recorded for males on each diet. Only one display was affected by parasite load. Highly parasitized males fed the nutritionally inferior diet juddered for a proportionately shorter time than males with low parasite loads. Also, older males performed juddering and shaking antennae proportionally longer and juddering and raising wings for longer durations than younger males. Males that successfully mated were observed for performance of 8 post-copulatory guarding behaviour displays. None of the guarding behaviours were affected by parasite load. However, one display was affected by age, with older males performing guard turning for shorter durations than younger males. Results are discuss,ed in terms of the influence of parasites and age on female choice.

Effect of Different Forms of Poly o-Toluidine /Poly Vinyl Chloride Composites on Dielectric Propertiesin the Microwave Field

In this paper we report the preparation and dielectric properties of poly o-toluidine:poly vinyl chloride composites in pellet and film forms. The composites were prepared using ammonium persulfate initiator and HCl dopant. The characterization is done by TGA and DSC. The dielectric properties including dielectric loss, conductivity, dielectric constant, dielectric heating coefficient, absorption coefficient, and penetration depth were studied in the microwave field. An HP8510 vector network analyzer with rectangular cavity resonator was used for the study. Sbands (2-4 GHz), C band (5-8 GHz), and X band (8-12 GHz) frequencies were used in the microwave field. Comparisons between the pellet and film forms of composites were also included. The result shows that the dielectric properties in the microwave field are dependent on the frequency and on the method of preparation.

The Importance of Agriculture-Dominated Landscapes and Lack of Field Border Effect for Early-Succession Songbird Nest Success

In recent decades, many early-succession songbird species have experienced severe and widespread declines, which often are related to habitat destruction. Field borders create additional or enhance existing early-succession habitat on farmland. However, field border shape and the landscape context surrounding farms may influence the effectiveness of field borders in contributing to the stabilization or increase of early-succession bird populations. We examined the influence of linear and nonlinear field borders on farms in landscapes dominated by either agriculture or forests on nest success and Brown-headed Cowbird (Molothrus ater) brood parasitism of Indigo Bunting (Passerina cyanea) and Blue Grosbeak (Passerina caerulea) nests combined. Field border establishment did not affect nest survival probability and brood parasitism frequency of Indigo Bunting and Blue Grosbeak nests. Indigo Bunting/Blue Grosbeak nest success probability was more than twice as high in agriculture-dominated landscapes (39%) than in forested landscapes (17%), and brood parasitism frequency was high (33%) but did not differ between landscapes. Edges in agriculture-dominated landscapes can be higher-quality habitats for early-succession birds than edges in forest-dominated landscapes, but our field border treatments did not enhance nest success for these birds on farms in either landscape.

The effect of flow field & geometry on the dynamic contact angle

A number of recent experiments suggest that, at a given wetting speed, the dynamic contact angle formed by an advancing liquid-gas interface with a solid substrate depends on the flow field and geometry near the moving contact line. In the present work, this effect is investigated in the framework of an earlier developed theory that was based on the fact that dynamic wetting is, by its very name, a process of formation of a new liquid-solid interface (newly “wetted” solid surface) and hence should be considered not as a singular problem but as a particular case from a general class of flows with forming or/and disappearing interfaces. The results demonstrate that, in the flow configuration of curtain coating, where a liquid sheet (“curtain”) impinges onto a moving solid substrate, the actual dynamic contact angle indeed depends not only on the wetting speed and material constants of the contacting media, as in the so-called slip models, but also on the inlet velocity of the curtain, its height, and the angle between the falling curtain and the solid surface. In other words, for the same wetting speed the dynamic contact angle can be varied by manipulating the flow field and geometry near the moving contact line. The obtained results have important experimental implications: given that the dynamic contact angle is determined by the values of the surface tensions at the contact line and hence depends on the distributions of the surface parameters along the interfaces, which can be influenced by the flow field, one can use the overall flow conditions and the contact angle as a macroscopic multiparametric signal-response pair that probes the dynamics of the liquid-solid interface. This approach would allow one to investigate experimentally such properties of the interface as, for example, its equation of state and the rheological properties involved in the interface’s response to an external torque, and would help to measure its parameters, such as the coefficient of sliding friction, the surface-tension relaxation time, and so on.

The effect of organic materials on the mobility and toxicity of metals in contaminated soils

Organic materials such as compost are often proposed as suitable materials for the remediation of contaminated brownfield sites intended for soft end-use. In addition to vitalising the soil, they are also believed to immobilise metals thereby breaking contaminant-receptor pathways and reducing the ecotoxicity of the contaminants. However, some research has demonstrated contradictory effects between composts on metal immobilisation. In the present study, four different composts and a liming product containing organic matter (LimeX70) were tested to examine both their metal retention and toxicity reduction capabilities on three different metal contaminated soils. Leaching tests, a plant growth test with Greek cress (Lepidium sativum), an earthworm (Eisenia fetida) survival and condition test and a bacterial toxicity test using Vibrio fischeri were carried out. The leaching test results showed that spent mushroom compost caused an increase in metal concentration in the leachates, while LimeX70 caused a decrease. The variation in behaviour between different amendments for each soil was high, so a generic conclusion could not be drawn. Toxicity tests showed significant reduction of metal bioavailability and toxicity for Greek cress, earthworms and bacteria. The results also suggest that more research should be undertaken to understand the mechanisms involved in metal complexation using different types of organic matter, in order to optimise the use of organic materials like compost for soil remediation. Crown Copyright (C) 2007 Published by Elsevier Ltd. All rights reserved.

Effect of manure application on crop yield and soil chemical properties in a long-term field trial of semi-arid Kenya

The sustainability of cereal/legume intercropping was assessed by monitoring trends in grain yield, soil organic C (SOC) and soil extractable P (Olsen method) measured over 13 years at a long-term field trial on a P-deficient soil in semi-arid Kenya. Goat manure was applied annually for 13 years at 0, 5 and 10 t ha(-1) and trends in grain yield were not identifiable because of season-to-season variations. SOC and Olsen P increased for the first seven years of manure application and then remained constant. The residual effect of manure applied for four years only lasted another seven to eight years when assessed by yield, SOC and Olsen P. Mineral fertilizers provided the same annual rates of N and P as in 5 t ha(-1) manure and initially ,gave the same yield as manure, declining after nine years to about 80%. Therefore, manure applications could be made intermittently and nutrient requirements topped-up with fertilizers. Grain yields for sorghum with continuous manure were described well by correlations with rainfall and manure input only, if data were excluded for seasons with over 500 mm rainfall. A comprehensive simulation model should correctly describe crop losses caused by excess water.

Enhanced phytoextraction: I. Effect of EDTA and citric acid on heavy metal mobility in a calcareous soil

Phytoextraction, the use of plants to extract heavy metals from contaminated soils, could be an interesting alternative to conventional remediation technologies. However, calcareous soils with relatively high total metal contents are difficult to phytoremediate due to low soluble metal concentrations. Soil amendments such as ethylene diaminetetraacetate (EDTA) have been suggested to increase heavy metal bioavailability and uptake in aboveground plant parts. Strong persistence of EDTA and risks of leaching of potentially toxic metals and essential nutrients have led to research on easily biodegradable soilamendments such as citric acid. In our research, EDTA is regarded as a scientific benchmark with which degradable alternatives are compared for enhanced phytoextraction purposes. The effects of increasing doses of EDTA (0.1, 1, 10 mmol kg(-1) dry soil) and citric acid (0.01, 0.05,0.25,0.442, 0.5 mol kg(-1) dry soil) on bioavailable fractions of Cu, Zn, Cd, and Pb were assessed in one part of our study and results are presented in this article. The evolution of labile soil fractions of heavy metals over time was evaluated using water paste saturation extraction (similar to soluble fraction), extraction with 1 M NH4OAc at pH 7 (similar to exchangeable fraction), and extraction with 0.5 M NH4OAc + 0.5 M HOAc + 0.02 M EDTA atpH 4.65 (similar to potentially bioavailable fraction). Both citric acid and EDTA produced a rapid initial increase in labile heavy metal fractions. Metal mobilization remained constant in time for soils treated with EDTA, but metal fractions was noted for soils treated with citric acid. The half life of heavy metal mobilization by citric acid varied between 1.5 and 5.7 d. In the following article, the effect of heavy metal mobilization on uptake by Helianthus annutis will be presented.

The effect of organic materials on the mobility and toxicity of metals in contaminated soils

Organic materials such as compost are often proposed as suitable materials for the remediation of contaminated brownfield sites intended for soft end-use. In addition to vitalising the soil, they are also believed to immobilise metals thereby breaking contaminant-receptor pathways and reducing the ecotoxicity of the contaminants. However, some research has demonstrated contradictory effects between composts on metal immobilisation. In the present study, four different composts and a liming product containing organic matter (LimeX70) were tested to examine both their metal retention and toxicity reduction capabilities on three different metal contaminated soils. Leaching tests, a plant growth test with Greek cress (Lepidium sativum), an earthworm (Eisenia fetida) survival and condition test and a bacterial toxicity test using Vibrio fischeri were carried out. The leaching test results showed that spent mushroom compost caused an increase in metal concentration in the leachates, while LimeX70 caused a decrease. The variation in behaviour between different amendments for each soil was high, so a generic conclusion could not be drawn. Toxicity tests showed significant reduction of metal bioavailability and toxicity for Greek cress, earthworms and bacteria. The results also suggest that more research should be undertaken to understand the mechanisms involved in metal complexation using different types of organic matter, in order to optimise the use of organic materials like compost for soil remediation. Crown Copyright (C) 2007 Published by Elsevier Ltd. All rights reserved.

Field studies on the effect of built forms on urban wind environments

Airflow through urban environments is one of the most important factors affecting human health, outdoor and indoor thermal comfort, air quality and the energy performance of buildings. This paper presents a study on the effects of wind induced airflows through urban built form using statistical analysis. The data employed in the analysis are from the year-long simultaneous field measurements conducted at the University of Reading campus in the United Kingdom. In this study, the association between typical architectural forms and the wind environment are investigated; such forms include: a street canyon, a semi-closure, a courtyard form and a relatively open space in a low-rise building complex. Measured data captures wind speed and wind direction at six representative locations and statistical analysis identifies key factors describing the effects of built form on the resulting airflows. Factor analysis of the measured data identified meteorological and architectural layout factors as key factors. The derivation of these factors and their variation with the studied built forms are presented in detail.

The effect of the magnetic field of the secondary star in dwarf novae

We investigate the effect of a secondary star magnetic field on the accretion disc dynamics of dwarf novae. Simulations have been carried out with a particle code and a dipolar magnetic field structure. The magnetic field acts to remove angular momentum from the disc material, increasing the inward mass flow. This makes the accretion disc more centrally condensed, causing a reduction in the recurrence time for dwarf nova outbursts. We have produced Doppler tomograms and light curves which may be compared with observations. These tomograms are significantly different from those produced in the absence of a magnetic field on the secondary. We derive an upper limit to the magnetic moment of the secondary star in UGem of mu_2<2x10^32 A m^2. The magnetic truncation of the accretion disc produces resonance phenomena similar to those seen in the superoutbursts of SUUMa systems. While these have not been observed for systems like UGem, observations of the SUUMa systems provide us with a useful diagnostic of the disc-field interaction. We are able to place an upper limit on the magnetic moment of the secondary in ZCha of mu_2<1x10^30 A m^2.

The effect of electric field direction on the-shear stress of ER fluids

The effect of the direction of external electric field on the shear stress of an ER fluid has been studied by molecular-dynamics simulation. Due to the formation of inclined chains, the shear stress strongly depends on the direction of the field, and it may be very large under some special field direction. And theoretical model of ideal microstructure of ER fluids has proved this result. Thus the ER effect may be greatly enhanced just by choosing an optimum direction for the field without any additional requirement, suggesting a promising way to the practical application of ER fluids.

Interactive effect of floral abundance and semi-natural habitats on pollinators in field beans (Vicia faba)

Pollination services are economically important component of agricultural biodiversity which enhance the yield and quality of many crops. An understanding of the suitability of extant habitats for pollinating species is crucial for planning management actions to protect and manage these service providers. In a highly modified agricultural ecosystem, we tested the effect of different pollination treatments (open, autonomous self- and wind-pollination) on pod set, seed set, and seed weight in field beans (Vicia faba). We also investigated the effect of semi-natural habitats and flower abundance on pollinators of field beans. Pollinator sampling was undertaken in ten field bean fields along a gradient of habitat complexity; CORINE land cover classification was used to analyse the land use patterns between 500–3000 m around the sites. Total yield from open-pollination increased by 185% compared to autonomous self-pollination. There was positive interactive effect of local flower abundance and cover of semi-natural habitats on overall abundance of pollinators at 1500 and 2000 m, and abundance of bumblebees (Bombus spp.) at 1000–2000 m. In contrast, species richness of pollinators was only correlated with flower abundance and not with semi-natural habitats. We did not find a link between pod set from open-pollination and pollinator abundance, possibly due to variations in the growing conditions and pollinator communities between sites. We conclude that insect pollination is essential for optimal bean yields and therefore the maintenance of semi-natural habitats in agriculture-dominated landscapes should ensure stable and more efficient pollination services in field beans.